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Fix infinite recursion on infinite types.

    This solves the occur check problem.

--- a/parse/infer.c

+++ b/parse/infer.c

@@ -249,6 +249,18 @@

     return (a->type == Tyvar && a->nsub > 0) || a->type == Tyarray || a->type == Tyslice;

 }

+static int occurs(Type *a, Type *b)

+{

+    size_t i;

+

+    if (a == b)

+        return 1;

+    for (i = 0; i < b->nsub; i++)

+        if (occurs(a, b->sub[i]))

+            return 1;

+    return 0;

+}

+

 static Type *unify(Node *ctx, Type *a, Type *b)

 {

     Type *t;

@@ -272,6 +284,10 @@

         tytab[a->tid] = b;

         r = b;

     }

+    if (b->type != Tyvar) 

+        if (occurs(a, b))

+            fatal(ctx->line, "Infinite type %s in %s near %s", tystr(a), tystr(b), ctxstr(ctx));

+

     if (a->type == b->type || idxhacked(&a, &b)) {

         for (i = 0; i < b->nsub; i++) {

             /* types must have same arity */

--- a/test/tests

+++ b/test/tests

@@ -40,3 +40,4 @@

 F declmismatch

 F infermismatch

 F flow

+F occur